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Purpose: We carried out a randomized, clinical trial in adults of both sexes with metabolic syndrome (MS) to assess the efficacy of high-intensity, low-volume interval training (HIIT) compared to moderate-intensity continuous training (MICT) on insulin resistance (IR), muscle mass, muscle activation, and serum musclin. Methods: Fasting glycemia, insulinemia, and glycated haemoglobin were determined by conventional methods, IR by Homeostatic model assessment (HOMA), lean mass by Dual-Energy X-ray Absorptiometry, muscle activation through carnosine by Proton Magnetic Resonance Spectroscopy, and musclin by Enzyme-Linked ImmunoSorbent Assay before and after a supervised, three-times/week, 12-week treadmill programme. HIIT (n = 29) consisted of six intervals with one-minute, high-intensity phases at 90% of peak oxygen consumption (VO2peak). MICT (n = 31) trained at 60% of VO2peak for 30 min. Results: Patients had a mean age of 50.8 ± 6.0 years, body mass index of 30.6 ± 4.0 kg/m2, and VO2peak of 29.0 ± 6.3 mL.kg−1.min−1. Compared to MICT, HIIT was not superior at reducing Ln HOMA-IR (adjusted mean difference: 0.083 [95%CI − 0.092 to 0.257]), carnosine or musclin or at increasing thigh lean mass. HIIT increased carnosine by 0.66 mmol/kg.ww (95% CI 0.08–1.24) after intervention. Both interventions reduced IR, body fat percentage and increased total lean mass/height2 and VO2peak. Musclin showed a non-significant reduction with a small effect size after both interventions. Conclusion: Compared to MICT, HIIT is not superior at reducing IR, carnosine or musclin or at increasing skeletal muscle mass in adults with MS. Both training types improved IR, muscle mass and body composition. NCT03087721, March 22nd, 2017. Trial registration number: NCT03087721. Registered March 22nd, 2017. [ABSTRACT FROM AUTHOR]

Background: We studied whether musclin function in humans is related to glycemic control, body composition, and cardiorespiratory capacity. Methods: A cross-sectional study was performed in sedentary adults with or without metabolic syndrome (MS). Serum musclin was measured by enzyme-linked immunosorbent assay. Insulin resistance (IR) was evaluated by the homeostatic model assessment (HOMA-IR). Body composition was determined by dual-energy X-ray absorptiometry and muscle composition by measuring carnosine in the thigh, a surrogate of fiber types, through proton magnetic resonance spectroscopy. Cardiorespiratory capacity was assessed through direct ergospirometry. Results: The control (n=29) and MS (n=61) groups were comparable in age (51.5±6.5 years old vs. 50.7±6.1 years old), sex (72.4% vs. 70.5% women), total lean mass (58.5%±7.4% vs. 57.3%±6.8%), and peak oxygen consumption (VO2peak) (31.0±5.8 mL O2./kg.min vs. 29.2±6.3 mL O2/kg.min). Individuals with MS had higher body mass index (BMI) (30.6±4.0 kg/m2 vs. 27.4± 3.6 kg/m2), HOMA-IR (3.5 [95% confidence interval, CI, 2.9 to 4.6] vs. 1.7 [95% CI, 1.1 to 2.0]), and musclin (206.7 pg/mL [95% CI, 122.7 to 387.8] vs. 111.1 pg/mL [95% CI, 63.2 to 218.5]) values than controls (P˂0.05). Musclin showed a significant relationship with HOMA-IR (β=0.23; 95% CI, 0.12 to 0.33; P˂0.01), but not with VO2peak, in multiple linear regression models adjusted for age, sex, fat mass, lean mass, and physical activity. Musclin was significantly associated with insulin, glycemia, visceral fat, and regional muscle mass, but not with BMI, VCO2peak, maximum heart rate, maximum time of work, or carnosine. Conclusion: In humans, musclin positively correlates with insulinemia, IR, and a body composition profile with high visceral adiposity and lean mass, but low body fat percentage. Musclin is not related to BMI or cardiorespiratory capacity. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to compare the effects of low-volume, high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT) on body composition in adults with metabolic syndrome (MS). Methods: This is a post hoc analysis of the randomized clinical trial Intraining-MET. Sixty adults (40–60 years old) were randomized to an MICT (n = 31) or HIIT (n = 29) supervised programme 3 days/week for 12 weeks. MICT sessions were conducted for 36 min at 60% of peak oxygen consumption (VO2peak). HIIT sessions included 6 intervals at 90% VO2peak for 1 min, followed by 2 min at 50% VO2peak. Body composition was assessed with dual energy X-ray absorptiometry. Results: Body weight did not change from pre- to post-training in either MICT (78.9 ± 15.6 kg; 77.7 ± 16.5 kg, p = 0.280) or HIIT groups (76.3 ± 13.4 kg; 76.3 ± 13.7 kg, p = 0.964). Body fat percentage and fat mass (FM) decreased post-training in the MICT (−0.9%; 95% confidence interval [CI]: −0.27 to −1.47 and −0.7 kg; 95% CI: −0.12 to −1.30) and HIIT groups (−1.0%; 95% CI: −0.32 to −1.68 and −0.8 kg; 95% CI: −0.17 to −1.47). Compared to the HIIT programme, MICT significantly reduced android FM (−0.14 kg; 95% CI: −0.02 to −0.26). Lean mass (LM) increased post-training in MICT (+0.7 kg; 95% CI: 0.01–1.41) and HIIT groups (+0.9 kg; 95% CI: 0.12–1.64), but only HIIT increased the trunk LM (+0.6 kg; 95% CI: 0.06–1.20). Conclusions: Both MICT and HIIT reduced FM without changing body weight in adults with MS. MICT had additional benefits by reducing the android FM, whereas HIIT seemed to increase LM. Given the characteristics of the post hoc analysis, further research is required to confirm these results. [ABSTRACT FROM AUTHOR]